The invention relates to a melting furnace wherein the movement of the consumable electrode is controlled according to the weight of the electrode, the electrode mounting passes through the furnace wall and is disposed for longitudinal movement, the furnace has a crossbeam that can be moved in the direction of feed and holds the electrode mounting, and the furnace has an auxiliary cylinder acting on the mounting and actuated by the pressure in the melting chamber, plus a sensor for measuring the weight of the consumable electrode.
The weight data can be used for current or power programming, for pressure programming, and the like. Controlling the melting rate via the continuous measurement of the weight of charges is often preferred because the other data usable for control, such as the electrode travel, are unreliable with respect to the melting rate, which is what must be controlled. Experience shows that determining the reduction of the weight of the charge per unit time, i.e., computing the quotients of the differences for regulating and control purposes, leads to a great uniformity of the melting process. German Patent 1758971 discloses the association of a force-dependent resistance with a point on the melting system which is under the influence of the consumable electrode weight, and the feeding of the electrical data thus obtained through an amplifier and a difference detector to an apparatus for controlling the melting rate. Since the unsteady friction forces falsely reflect an irregular melting rate and produce regulating actions which can overdo the process, compensating means are already provided in the known apparatus. Furthermore, in U.S. Pat. No. 3,272,905 it is proposed to apply the feed rate detectors to the points of transition between the feed system and the electrode holder. In this manner the friction forces at a gasket that may be present are indeed not measured by the weight detector, but the detector is in the interior of the furnace where it is exposed to the effect of heat, and the current, which can amount to thousands of amperes, flows through it. Moreover, in the case of great electrode weights, and the leverage which the electrode has, such a detector is hardly able to withstand such severe operating conditions, and this again leads to a considerable loss of accuracy of measurement. Also, an intensive water cooling of the detector is essential.
Now, it is the aim of the present invention to create a weight-related control apparatus for a melting furnace, which will be capable of lowering an electrode or consumable electrode of especially great weight and large diameter with great sensitivity into the melting chamber, which is under high pressure. In particular, the weight of the electrode, which varies during the melting process, is to be registrable within very narrow limits, so that the melting process will remain precisely controllable in all phases.